听说微信改用了speex, 于是今天访问了speex网站：
发现从08年的Speex 1.2rc1之后，在2014年12月份和2015年1月份更新了两次
根据说明，是说对resampler做了NEON指令的优化，我记得案桌里面就带有speex的resampler的NEON版本（不过还是不如我们自己优化的快），不知道为什么speex.org刚刚更新。
每个codec都宣称自己很好，比如speex说：
Speex is based on CELP and is designed to compress voice at bitrates ranging from 2 to 44 kbps. Some of Speex's features include:
- Narrowband (8 kHz), wideband (16 kHz), and ultra-wideband (32 kHz) compression in the same bitstream
- Intensity stereo encoding
- Packet loss concealment
- Variable bitrate operation (VBR)
- Voice Activity Detection (VAD)
- Discontinuous Transmission (DTX)
- Fixed-point port
- Acoustic echo canceller
- Noise suppression
Note that Speex has a number of features that are not present in other codecs, such as intensity stereo encoding, integration of multiple sampling rates in the same bitstream (embedded coding), and a VBR mode; see our comparison page for more.
对于speex 1.2 rc1的说明是：
This release adds support for acoustic echo cancellation with multiple microphones and multiple loudspeakers. It also adds an API to decorrelate loudspeaker signals to improve multi-channel performance. In the bugfix department, there are fixes for a few bugs in the echo canceller, jitter buffer and preprocessor. At this point, the API for 1.2 should be stable and only a few very minor additions are planned
是支持双麦克回声抵消么？ 很想测测看效果怎么样。。
不知道和后来的codec比，比如SILK, OPUS, EVS之间的效果怎么样？
需要比较一下么？